Genetic Recombination Overview
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What is the primary mechanism required for homologous recombination?

  • Identical DNA fragments
  • Extensive sequence similarity (correct)
  • Unique DNA recognition sequences
  • Random DNA segments

    • Site-specific recombination requires extensive homology between DNA segments.

    False

    Name a reconbinase enzyme involved in site-specific recombination.

    Cre

    The process that ensures genetic diversity during meiosis is called ______.

    <p>homologous recombination</p> Signup and view all the answers

    Match the type of recombination with its characteristic:

    <p>Homologous recombination = Requires extensive sequence similarity Site-specific recombination = Involves unique recognition sequences</p> Signup and view all the answers

    Which of the following best describes the biological function of homologous recombination?

    <p>Repair of double-stranded DNA breaks</p> Signup and view all the answers

    RecA is a protein used in mechanism of homologous recombination in bacteria.

    <p>True</p> Signup and view all the answers

    What biological function is associated with site-specific recombination?

    <p>Integration of viral genomes into host DNA</p> Signup and view all the answers

    What is the purpose of RecBCD in the repair process?

    <p>To create a recombinogenic end</p> Signup and view all the answers

    Holliday junctions can only produce crossover products.

    <p>False</p> Signup and view all the answers

    What does RecA bind to in the process of homologous recombination?

    <p>Single-stranded DNA (ssDNA)</p> Signup and view all the answers

    The Chi sequence is recognized by RecC and alters the behavior of the RecBCD complex, reducing degradation of the ______ strand.

    <p>3'</p> Signup and view all the answers

    Match the following components with their functions in homologous recombination:

    <p>RecBCD = Creates a recombinogenic end RecA = Promotes strand invasion Resolvases = Resolve Holliday junctions Chi sequence = Hotspots for recombination</p> Signup and view all the answers

    Which statement is true regarding the resolution of Holliday junctions?

    <p>Specific enzymes called resolvases are involved.</p> Signup and view all the answers

    What is a key feature of the RecBCD complex in the context of homologous recombination?

    <p>It unwinds DNA at a high speed to create single-stranded tails.</p> Signup and view all the answers

    What is the primary outcome of the Cre-Lox system?

    <p>Insertion, deletion, or inversion of DNA segments</p> Signup and view all the answers

    Sister chromatid exchange (SCE) leads to genetic diversity.

    <p>False</p> Signup and view all the answers

    What type of DNA structure forms during the process of recombination known as the Holliday Junction?

    <p>Four-stranded DNA structure</p> Signup and view all the answers

    Sister chromatid exchange mainly occurs during ________ as a repair mechanism.

    <p>mitosis</p> Signup and view all the answers

    Match the processes to their descriptions:

    <p>Recombination in Meiosis = Involves non-identical chromatids and increases genetic diversity Sister Chromatid Exchange = Occurs between identical sister chromatids for repair Holliday Junction Formation = Involves alignment of two double-stranded DNA molecules DNA Replication = Mechanism of copying DNA to produce two identical copies</p> Signup and view all the answers

    What is a key difference between recombination in meiosis and mitosis?

    <p>Meiosis involves non-identical chromatids while mitosis involves identical chromatids</p> Signup and view all the answers

    BrdU can be used to visualize sister chromatid exchanges in cells.

    <p>True</p> Signup and view all the answers

    What is the role of recombination in meiosis?

    <p>Increase genetic diversity</p> Signup and view all the answers

    The genetic recombination process is the breaking and ________ of DNA.

    <p>rejoining</p> Signup and view all the answers

    What is the primary function of sister chromatid exchange?

    <p>Repairing DNA damage</p> Signup and view all the answers

    What is the primary outcome of homology-directed repair in the context of DNA?

    <p>Exact repair and recombination of DNA</p> Signup and view all the answers

    Spontaneous branch migration occurs rapidly and effectively without any external assistance.

    <p>False</p> Signup and view all the answers

    What role does RuvB play in bacterial branch migration?

    <p>It forms a molecular motor that unwinds and moves the junction along DNA.</p> Signup and view all the answers

    The process by which one strand of DNA invades a homologous DNA molecule is called __________.

    <p>strand invasion</p> Signup and view all the answers

    Match the proteins involved in branch migration with their respective organisms:

    <p>RuvA = Bacteria RuvB = Bacteria RAD51 = Eukaryotes Associated Proteins = Eukaryotes</p> Signup and view all the answers

    What is a primary function of meiotic recombination?

    <p>Increases genetic diversity</p> Signup and view all the answers

    The D-loop is formed during strand invasion when a 5' overhang pairs with the complementary strand of DNA.

    <p>False</p> Signup and view all the answers

    What happens to the DNA at the double-strand break during the processing phase?

    <p>Exonuclease activity degrades the DNA, creating single-stranded 3' overhangs.</p> Signup and view all the answers

    Efficient branch migration is essential for maintaining __________ stability.

    <p>genome</p> Signup and view all the answers

    In what context might a double-strand break (DSB) occur?

    <p>Due to programmed breaks or damage</p> Signup and view all the answers

    What is formed when two single DNA strands exchange partners during crossing over?

    <p>Holliday junction</p> Signup and view all the answers

    Branch migration is a static process that does not change the length of the heteroduplex region.

    <p>False</p> Signup and view all the answers

    What enzyme resolves the Holliday junction in eukaryotes?

    <p>GEN1</p> Signup and view all the answers

    The process of _____ occurs when single-strand breaks in homologous DNA molecules lead to strand invasion.

    <p>crossing over</p> Signup and view all the answers

    Match the following stages of Holliday junction formation to their descriptions:

    <p>Single-strand breaks = Nicked strands in homologous DNA Strand invasion = Nicked strands pair with complementary strands Crossing over = Exchange of DNA partners Resolution = Cleaving of the Holliday junction</p> Signup and view all the answers

    What structure do the DNA arms of the Holliday junction form when viewed from the side?

    <p>Stacked X shape</p> Signup and view all the answers

    Holliday junctions are initially four-fold symmetrical and can also adopt a stacked-X conformation.

    <p>True</p> Signup and view all the answers

    What is the role of divalent cations like magnesium (Mg^2+) in relation to Holliday junctions?

    <p>Increase stability</p> Signup and view all the answers

    In the resolution process, the Holliday junction can result in _____ products where chromosomes exchange large DNA segments.

    <p>crossover</p> Signup and view all the answers

    Which of the following correctly describes single-strand breaks in the context of DNA recombination?

    <p>They occur at similar positions in two homologous DNA molecules.</p> Signup and view all the answers

    Study Notes

    Genetic Recombination

    • Genetic recombination is the process of breaking and rejoining DNA segments.
    • It enables new combinations of genetic material.

    Two Types of Recombination

    • Homologous Recombination

      • Involves exchanging DNA segments between similar or identical DNA molecules.
      • Requires significant sequence similarity (homology) between the segments.
      • Uses general recombination proteins like RecA (bacteria) and RecBCD (bacteria, eukaryotes) to process DNA.
      • Repair double-stranded DNA breaks and maintain genome integrity.
      • Essential for genetic diversity during meiosis and crossover events.
      • Results in an exchange between homologous regions, often producing crossover products.

    • Site-specific Recombination

      • Involves exchanging DNA at specific recognition sequences.
      • Uses short, unique sequences.
      • Relies on specific recombinase enzymes (e.g., Cre in the Cre-Lox system, or integrases).
      • Does not rely on extensive homology.
      • Important in biological functions such as viral genome integration.

    Recombination in Meiosis I

    • Sister Chromatid Exchange (SCE)
      • Involves the exchange of genetic material between identical sister chromatids during mitosis, used for DNA repair.
      • Does not contribute to genetic diversity.

    Holliday Junctions

    • A four-stranded DNA structure formed when homologous or nearly identical DNA molecules align.
    • This structure is important for various genomic processes.

    Formation Process (Holliday Junction)

    • Involves strand invasion and branch migration.
    • Involves specific enzymes to resolve the junctions (e.g., RuvC in bacteria).
    • Results in non-crossover or crossover products depending on cleavage of the junction.
    • Non-crossover products—no substantial exchange of genetic material.

    Branch Migration

    • A process where the Holliday junction moves along the DNA.
    • Driven by enzymes like RuvAB in bacteria.
    • Important in DNA repair and recombination.

    Stacked-X Conformation

    • This is a key structural feature of Holliday junctions that is adopted under various conditions within a cell.
    • This conformation involves stacking base pairs and folded arms.
    • There are two types of strands in this conformation
    • Continuous
    • Exchanging

    Double-strand Break Repair (DSBR) Model

    • A model describing how double-strand breaks in DNA are repaired.
    • Involves strand invasion and repair synthesis.

    Homologous Recombination in E. Coli

    • The steps in homologous recombination in E.coli are described.
      • Pre-junction formation
      • Post-junction formation
    • This is a key mechanism for ensuring robust DNA repair in E. coli.

    RecBCD

    • A complex composed of several components with key functions relevant to DNA metabolism

    RecA

    • A key protein that is involved in many steps of homologous recombination.

    RuvA and RuvB

    • Proteins that are important in the branch migration part of the process of homologous recombination in bacteria.

    RuvC

    • A specific enzyme that is involved in the resolution of Holliday junctions.
    • Targeted to DNA junctions.

    Homologous Recombination in Yeast

    • Five key steps in homologous recombination in yeast are detailed.
      • Double-strand break formation
      • Overhang formation
      • Filament formation
      • Holliday junction formation
      • Resolution of Holliday junctions.

    Filament Creation

    • A single-stranded DNA overhang formed at the broken site.
    • Key proteins such as RAD51 play important roles.

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    Related Documents

    Genetic Recombination PDF

    Description

    Explore the fascinating processes of homologous and site-specific genetic recombination. Learn about the mechanisms involved, key enzymes, and the significance of these processes in genetic diversity and DNA repair.

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